1. Field of the Invention
The present invention relates to an ink amount detecting device for informing of the shortage of ink remainder in a printing apparatus or the like of an ink jet type, for example.
2. Related Background Art
As means for detecting a shortage of the amount of ink remainding in a printing apparatus using a liquid ink as a recording agent, there has hitherto been available, among various others, a method for detecting the surface of the liquid ink liquid utilizing the electrical conductivity of the ink by providing a pair of electrodes in an ink tank; a method for detecting by a pressure sensor the negative pressure which is generated when the ink is exhausted from an ink container having a flexible bag; or a method for optically detecting the position of a float which floats in the tank using an infrared light which passes through the tank wall. Among them, the method for optically detecting the float position is particularly desirable and excellent from the viewpoint of apparatus maintenance because this method is of the non-contact type and there is no need for embedding any detecting members in the tank or in the ink guiding passage unlike other methods.
Nevertheless, since this optical detection method uses a float, in some cases binding or sticking occurs between the tank wall and the float, leading to a significant drawback such as lowering the reliability.
Also, in a case of a printing apparatus of a serial type which records by allowing the recording head to scan a recording sheet, the ink container is arranged to move along with the recording head. Thus, it is necessary to provide a mechanism to detect the ink remainder in such a movable ink container, which creates a problem in making the recording head portion small and light, the wiring arrangement simple, or the like, leading to the complicated structure of the apparatus after all.